Re: [PATCH v4 2/2] media: i2c: ov02c10: Correct power-on sequence and timing

[Sakari Ailus <sakari.ailus@linux.intel.com>]

HI Saikiran,

On Tue, Jan 27, 2026 at 10:20:24PM +0530, Saikiran wrote:
> The previous power-on sequence did not strictly follow the hardware timing
> requirements (T1), potentially leading to initialization failures on some
> platforms.
> 
> Update the sequence to match the datasheet and maintainer recommendations:
> 1. Assert XSHUTDOWN (reset) for 5ms (T1 >= 5ms) before enabling power
>    resources.
> 2. Enable clock and regulators in the standard order.
> 3. De-assert XSHUTDOWN.
> 4. Wait 5ms (T2 >= 5ms) for sensor boot before I2C access (using a wider
>    range for timer coalescing).
> 
> This ensures the sensor enters a clean state during cold boot.
> 
> Tested-on: Lenovo Yoga Slim 7x (Snapdragon X Elite)
> Fixes: 44f8901 ("media: i2c: add OmniVision OV02C10 sensor driver")
> Cc: stable@vger.kernel.org
> Signed-off-by: Saikiran <bjsaikiran@gmail.com>
> ---
>  drivers/media/i2c/ov02c10.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/i2c/ov02c10.c b/drivers/media/i2c/ov02c10.c
> index fa7cc48b769a..3bfbd0deb126 100644
> --- a/drivers/media/i2c/ov02c10.c
> +++ b/drivers/media/i2c/ov02c10.c
> @@ -676,6 +676,12 @@ static int ov02c10_power_on(struct device *dev)
>  	struct ov02c10 *ov02c10 = to_ov02c10(sd);
>  	int ret;
>  
> +	/* Assert reset for 5ms to ensure sensor is in reset state */
> +	if (ov02c10->reset) {
> +		gpiod_set_value_cansleep(ov02c10->reset, 1);

Is this needed? Isn't XSHUTDOWN already asserted here?

> +		usleep_range(5000, 6000);
> +	}
> +
>  	ret = clk_prepare_enable(ov02c10->img_clk);
>  	if (ret < 0) {
>  		dev_err(dev, "failed to enable imaging clock: %d", ret);
> @@ -691,10 +697,8 @@ static int ov02c10_power_on(struct device *dev)
>  	}
>  
>  	if (ov02c10->reset) {
> -		/* Assert reset for at least 2ms on back to back off-on */
> -		usleep_range(2000, 2200);
>  		gpiod_set_value_cansleep(ov02c10->reset, 0);
> -		usleep_range(5000, 5100);
> +		usleep_range(5000, 5500);

According to the datasheet you seem to need 8192 XVCLK cycles after
deasserting XSHUTDOWN before proceeding with I²C access.

>  	}
>  
>  	return 0;

-- 
Regards,

Sakari Ailus